jan/feb 2003, page 76, the star:

'during heavy rain, water may enter the front passenger area through the bolt holes for the engine control module in the firewall. the water collects in the footwell near the o2 sensor and plug, causing corrosion. clean or replace the o2 sensor and plug as necessary, and seal the control module securing bolts in the firewall'

the water is tripping the check engine light.

anybody having interior moisture problems should check this out.



thank you stu ritter technical editor the star

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g-wagen

The above is very, very good advice.

I went to clear my persistent clogged EGR code 5 on the DM when I saw there was also a code 2 (inoperative Heated O2 Sensor). For the past few weeks I have experienced somewhat sluggish acceleration, somewhat erratic idle, and very noticeable pungent exhaust fumes.

Upon pulling back the carpet I saw a very small amount of water in footwell. But when I squeezed the insulation/padding, it was like squeezing a wet sponge. I also saw that the three-wire connector(s) for the O2 sensor was green with corrosion, the second white wire from the gray one being the originating point.

After thoroughly cleaning the connectors and reattaching, the erratic idle is gone (the dashboard looks like a photograph because the tach and oil pressure gauges don’t move); and acceleration is crisp again, whereas before it was kind of mushy/sluggish, like walking in slush. The fumes, however, though not as bad as they were a few days ago, are nonetheless still present, which directs me to replace the coolant temp sensor which I know is faulty. (Now I know why I’ve had daily headaches for the past month or so.)

It appears, however, the insulated floor mat, which is now sitting out in the sun, will take a few days to dry out. The water came in as described in the previous post, in a small trickle, except my entry point was where the cables/wires come through the firewall. windshield drains are clear, but the rubber guard piece at between the glass and the edge of the hood was somehow twisted out of place. It does not appear to be a heater core leak as there is nowhere near enough coolant loss to account for the amount of water in the padding – unless this has been going on and on for months, with the padding never drying out. But after running the heater, I saw no water leakage.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Correction:

It is raining here today and my passenger floor got wet. However, the trickle I described above is/was not the source of the flooding. Instead, the drain in the fender just in front of the passenger door was clogged, and water accumulating in the small reservoir at the bottom of the fender was backing up through a wire/cable opening, and into the passenger floor.

If you suspect this is your problem, feel around for a cone-shaped, rubber nipple under the fender, just ahead of the passenger door, then stick your finger up into it and clear any blockage.

For almost two years I wondered what the slow dripping from that area was after washing the car, or after it rained. It would persist for hours. After clearing the blockage, the water ran out like a faucet. Luckily, the bottom carpet with the foam padding was out of the car, otherwise it would take another three days to dry it out.

FYI: Since the wet under-carpet has been out of the car, the interior no longer smells like "breath" in wet/humid weather.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Thought I was done with this but only temporarily moved a blockage from over the drain hole, as I discovered as it rained all day today and I had another flood in the passenger footwell, soaking my O2 sensor connection and giving me crappy mileage and doggish performance. So here is what you need to do if you have this problem:

Use a hooked probe to go up into the drain, and pull the entire rubber stopper out. It is essentially a cone within a cone. The outer cone is a rubber funnel with a wide spout. The inner is a cone with three small holes in a triangular pattern. Small debris and sludge will easily clog them.

Use scissors to snip the rubber between each hole. You will then have a large triangular opening that water and small debris will easily flow through. Replace the stopper (I don’t know what else to call it) with the outer cone pointing back towards the rear of the car. Hopefully, that will do it. (And luckily, I have not yet replaced the lower carpet. After 7 days, is still not completely dry.)

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2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Eric,
Thanks for your post; I removed the fender plug from my 1993 300ce and it was completely clogged. I have removed it. Hopefully, the floor carpeting etc now will remain dry.
Regards

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87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)